1. Field of the Invention
The present invention relates to the structure of a pressure fluidized bed firing boiler disposed within a pressure vessel, for example, a support structure of a pressure fluidized bed firing boiler or a reinforcement structure of the pressure vessel, and more particularly to an improved structure of a pressure fluidized bed firing boiler which contributes to a down-sizing and reduction in weight thereof.
2. Description of the Prior Art
In a heretofore known structure for supporting a pressure fluidized bed firing boiler disposed within a pressure vessel, a system for suspending the entire load of a supporting object of the boiler main body from a support beam provided at within the pressure vessel has been employed.
However, in the case where such a system for suspending an entire load of a supporting object of the boiler main body from a support beam is employed, if the fluidized bed firing boiler is to have a large capacity, the support beam structure must be large and a load acting upon a shell of the pressure vessel is correspondingly large. Hence, there exists a problem in that a strong reinforcement structure for the shell is necessitated.
Also, in order to resolve such a problem, one can conceive of a system in which the entire load of the supporting object of a boiler main body is supported by a support beam provided under the pressure vessel. However, if such a system were employed in a large-capacity fluidized bed firing boiler, the compression load acting upon peripheral wall pipes of the boiler would become maximum, and hence the load could exceed the buckling strength of the vessel.
Further, in a heretofore known pressure fluidized bed firing boiler disposed within a vertical type pressure vessel, the fluidized bed main body accommodates an evaporator, a superheater and a reheater in the same furnace.
However, in such a fluidized bed main body, there exists a problem in that the combustion control means, provided as a countermeasure against the reheating of the tubes upon the starting of the pressure fluidized bed firing boiler, is complicated.
Furthermore, in the prior art, as a pressure vessel for containing a pressure fluidized bed firing boiler, though a cylindrical pressure vessel of a vertical type is known, a cylindrical pressure vessel of a horizontal type does not exist.
Now, in the case where a cylindrical pressure vessel of a horizontal type contains a pressure fluidized bed firing boiler, although a cylindrical cross section of the vessel can be maintained merely by the mechanical strength of a shell of the vessel when the vessel has a relatively small diameter, when the vessel has a large diameter and is extremely thin, a large flexure is generated in the circumferential direction of the cylindrical shell. Hence, the shell will deform into an elliptical shape, and there is a risk that the fluidized bed main body within the pressure vessel may be damaged.
In addition, a support system for supporting the fluidized bed main body and a frame structure serving as an operating scaffold must be provided within the vessel. Because many members are accordingly disposed in a narrow space, there are many restrictions in design, sometimes resulting in an uneconomical design. Such problems also must be resolved.